Our conscious life is one unceasing change. From the first awakening of consciousness to the actual present, no one moment has been the mere repetition of another, and the moments which as we look back seem to have made up our life are not separable elements of it but our own divisions of a change that has been continuous. And as it has been, so we know it will be until consciousness ceases with death. Consciousness and life are in this respect one and the same, although when we speak of our consciousness we think chiefly of a passive receptivity, and when we speak of our life we think of an activity. Consciousness as the unity of knowing and acting is a becoming. The past is not left behind, it is with us in the form of memory; the future is not a predetermined order which only a natural disability prevents us from knowing, it is yet uncreated; conscious life is the enduring present which grows with the past and makes the future. This reality of consciousness is our continually changing experience. But there is also another reality with which it seems to be in necessary relation and also in complete contrast--this is the reality of the material or physical universe. The world of physical reality seems to be composed of a matter that cannot change in a space that is absolutely unchangeable. This physical world seems made up of solid things, formed out of matter. Change in physical science is only a rearrangement of matter or an alteration of position in space. This physical reality is not, as psychical reality is, {16} known to us directly; it is an interpretation of our sense experience. Immediate experience has objects, generally called sense data. These objects are what we actually see in sensations of sight, what we actually hear in sensations of sound, and so on; and they lead us to suppose or infer physical objects--that is, objects that do not depend upon our experience for their existence, but whose existence is the cause of our having the experience. The process by which we infer the nature of the external world from our felt experience is logical. It includes perceiving, conceiving, thinking or reasoning. The object of the logical process, the aim or ideal to which it seeks to attain, is truth. Knowledge of reality is truth.